Footwear having soles of a varying porosity



Nov. 23, 1954 H. ROLLMAN 2,594,871

FOOTWEAR HAVING SOLES OF A VARYING POROSITY Filed Sept. 28, 1950 2 Sheets-Sheet l IN V EN TOR. HEIIVZ ROLL MAW AT T E/V5349 Filed Sept. 28. 1950 Nov. 23, 1954 H. ROLLMAN 2,694,871

FOOTWEAR HAVING SOLES OF A VARYING POROSITY 2 Sheets-Sheet 2 I panama-19mm ":zo'mcwanmd k \LVL INVEN TOR. HEl/VZ ,eoLmm/v A T TOWEMS United States Patent FOOTWEAR HAVING SOLES OF A VARYING POROSITY Heinz Rollman, Waynesville, N. C., assignor to Ro-Search Inc., Waynesville, N. C., a corporation of North Carolina Application September 28, 1950, Serial No. 187,320

3 Claims. (Cl. 36-14) This invention relates to footwear having soles of a varying porosity and has for an object to provide a shoe somewhat similar to the one disclosed in patent to Hans Rollmann 1,955,720, the sole being expanded and formed in situ in a mold, the sole however, being integral or monolithic and having its exposed surfaces formed of non porous rubber while the sole interior is formed of porous rubber, preferably of varying porosity.

Another object of the invention is to increase the resistance of such footwear to wear and tear and to increase at the same time the comfort offered to the wearer.

Another object is the provision of such a shoe in which the sole bottom and sides are formed of non-porous rubber while the sole interior is formed of porous rubber, preferably of varying porosity.

Other objects will become apparent from the following description taken in connection with the attached drawings showing several illustrative embodiments of the invention and wherein:

Fig. 1 is an exploded cross-section of a mold used for the manufacture of footwear according to the invention together with the component parts of the shoe;

Fig. 2 shows a cross-section of the mold and components of Fig. l, the mold being closed and the parts being in the condition in which they exist before vulcanization starts;

Fig. 3 is a perspective view of a cross-section of the shoe resulting from the vulcanizing process;

Fig. 4 is a perspective view similar to Fig. 1 but showing a modified form of mold adapted for another variation of filling the mold with the components of the sole;

Fig. 5 shows the mold and components of Fig. 4 after closing but before vulcanization starts;

Fig. 6 is an exploded view of a mold in cross-section adapted for the use of latex for at least part of the components of the sole, together with the components of the shoe; and

Fig. 7 shows the same mold, closed, during vulcanization.

According to the invention the sole, which might be part of a shoe, a slipper, a sandal, or any other type of footwear, has an interior of relatively high porosity which provides for the foot a soft and resilient cushion. The outer part of the sole is formed of non-porous or practically non-porous rubber and these two parts or sections of the sole are connected by a section or layer of gradually changing porosity. The thickness of the aforementioned sections varies according to the intended use of the shoe.

The upper 5 which may be cut in any desired manner consists of textile material or any other suitable sheet material, lined or unlined. The sole may be of the same constitution throughout its length or may differ at varying points, viz., as between the sole proper and the heel.

In the manufacture of footwear according to the invention (Figs. 13), the upper 5 is formed in known manner and is drawn upon a suitable last L. In this form of the invention the sole mold may be of the form shown at 1 consisting of a bottom plate 1a, an edge 1b, said edge being formed with a lip 1c against which the upper is pressed when the mold is closed. Placed within said sole mold with its edges turned up, more or less as shown in Figs. 1 and 2, is a blanked piece of rubber material 2 laminated in such a way that the upper or inner section contains a full portion of blowing agent such as ammonium carbonate. The outer layer contains no blowing agent but is otherwise preferably identical with the maice terial of the upper or inner section. One or more intermediate layers or sections contain gradually increasing amounts of blowing agent progressively from the outer toward the inner layers. This laminated sheet material 2 may be formed by properly milling and mixing separate thin sheets of rubber mix having respectively no blowing agent and gradually increasing amounts of blowing agent. These layers are then rolled together in their proper order and blanks of suitable size and shape are thereupon cut from the resultant laminated sheet. The thickness of the various sections or layers composing the laminated sheet 2. varies according to the intended use of the footwear but his important to provide for the gradual change from the high porosity section to the layer or section of solid rubber which forms the outside of the sole.

By using as the interior a rubber mix with high content of blowing agent and consequent high porosity in the resultant shoe, the desired cohesion of the sole to the upper is facilitated and the comfort of the wearer increased while, at the same time, the harder sole surface and edge lmproves the durability of the shoe. It is often desirable to use an insert 3 of medium stifi felt as shown and usually a top layer 4 of soft cotton.

Thereafter, the last L with the upper 5 and sock lining 6 (preferably connected by the seam 7) thereon is placed upon the mold so that the parts are in the position shown in Fig. 2. It will be noted that at this time the mold is not entirely filled by the parts mentioned. The last and mold are clamped together by a suitable clamping device (not shown) and the assembly is subjected to heat for a sufficient length of time to first cause the blowing agent to expand the various sections of the blank 2 to fill the mold under pressure and to then cause the rubber to be vulcanized. This expansion and vulcanization will cause the formation of the sole having a shape conforming to the shape of the mold and cause said sole to adhere to the upper so as to produce a product as shown in Fig. 3. It will be clear that the bottom section of the sole as well as the edges are formed of non-porous rubber, whereas the interior sections are formed of rubber of gradually increasing porosity.

As will be apparent from Fig. 2 of the drawing, the last L with the upper in place thereon bears firmly against the upper edge of the mold, so that upon the application of pressure the last and upper are caused to seat accurately upon the mold and the possible escape of the sponge rubber, due to the pressure generated as it swells during the vulcanization process, is prevented. It is usually desirable to have the last with the insole and the upper thereon spaced somewhat from the rubber mix when the parts are assembled, and prior to the vulcanization treatment, to allow expansion of the porous rubber material during vulcanization. In the construction shown, this is effected by reason of the formation of the last and mold, which prevents the last from being forced down onto the rubber mix in such a way that the mix would be displaced and distributed unevenly throughout the mold. Accurate and uniform results are thus obtained in every case, so that the product is free from undesired variations in thickness of the resultant sole.

If now the assembled parts are introduced into the vulcanizing chamber or if the last is heated internally and if necessary the sole mold heated externally, then simultaneously with the swelling and molding of the rubber contained in the mold, in accordance with the amount of blowing agent it contains, a firm joining of the sole with the upper is effected by the vulcanization, so that the sole is formed and in the same operation is simultaneously connected with the upper and insole to form the complete shoe.

The rubber mix which is comparatively plastic when being vulcanized and which is under considerable pressure due to the expansion thereof is forced into all parts and crevices in the mold and into the pores and interstices in and about that portion of the upper and insole or filler which is exposed thereto within the mold. This insures a very firm bonding of the sole and upper so that no cement, binding strip or foxing is required to hold the parts together.

In some instances, it is of advantage to fill the mold, as shown in Fig. 4, with more than one piece of rubber mix. For this purpose the mold may be composed of a bottom plate 8 and a frame 9 with a sharp edge 15 directed toward the bottom plate. In preparing the mold for vulcanization, a sheet '10 of laminated rubber, as described above, is placed upon the bottom plate 8 whereupon the frame 9 is placed upon that laminated sheet. Thereafter a strip 11 of similar, but not necessarily identical, laminated rubber is used to fill the side of the frame -9 and is held in place by inserting medium still felt 12. Soft cotton 13 may also be used. After the filling of the mold is completed the upper 14, mounted on last L, is used to close the mold in the way described above.-- The edge 15 of the frame 9 trims the bottom material of the sole under the closing pressure and the heat of vulcanization. After vulcanization the resultant shoe will be substantially identical with the one shown in Fig. 3, the porosity increasing gradually toward the interior.

Instead of using laminated sheets of rubber, I may place in the appropriate sequence single sheets of rubber containing blowing agents in varying degrees. As the effect of the blowing agent permeates into the adjoining rubber sections, the finished shoe will have an integral sole with gradually increasing porosity from the nonporous outside to the highly porous inside of the sole.

In some instances I prefer the use of rubber latex for at least a part of the sole components. As shown in Fig. 6, I may provide a mold frame ,25 resting upon the upper 26 mounted upon the last 27. The inside of the frame 25 is thereafter coated with one or more layers of latex 31 without blowing or foaming agent, ,the cotton insert 13 and the felt insert 12 are located over the sock lining 6 and foamed latex 28 .or latex containing a blowing agent is used to fill the remaining spaces in the mold. Anon-porous tread-sole 29 of rubber or a leather sole might then be placed upon the frame 25 before the .sole

plate 30 is clamped in place and the assembly subjected to heat and vulcanization as described above.

.In the foregoing, the term rubber has been ,used -to mean not only the product of the Hevea plant, but to meanany natural or synthetic elastomer of similar physical properties.

While preferred forms of the invention have been illustrated and described above, it will be apparent that numerous changes and modifications may be made in the form and arrangement of the parts employed and the mannerof producing boots, shoes, slippers and the like in accordance withmy invention withoutdeparting from the spirit and scope thereof.

What is claimed is: I

1. In an article of footwear a sole formed of rubber, said rubber having a varying porosity, said porosity changing gradually over a substantial part of the cross section of said sole from a lower porosity near the exterior of said sole to a substantially higher porosity near the interior of said sole.

2. In an article of footwear a sole with an exterior section of non-porous rubber connected to an internal section of sponge rubber by an intermediate section of sponge rubber of substantial thickness having a varying porosity, the porosity of said intermediate section changing gradually from a lower porosity near said external section to a substantially higher porosity near said internal section of said sole.

3. A boot, shoe or the like comprising an upper, an insole, and a rubber sole of varying porosity, said sole being expanded in situ and bonded to the insole and upper by vulcanization, the bottom and lateral edges of said sole being formed of non-porous rubber and the interior thereof being formed of a section of porous rubber connected to said non-porous section through an intermediate section of substantial thickness in which the rubber thereof changes gradually from higher porosity near the interior of said sole to lower porosity near said bottom and lateral edges.

References Cited in the file ,of this patent UNITED STATES PATENT-S Nu ame Da 1,499,166 Frazier June 24, 1924 1,533,008 Keiser Apr. 7, 1925 1,624,500 Murray Apr 12, 1927 1,843,893 Becher Feb. 2, 1932 1,955,720 Rollrnann Apr. 17, 1934 1,961,745 Eckhardt June 5, 1934 2,129,106 Szerenyi Sept. 6, 1938 2,163,289 Pennell et' al. June 20, 1939 2 384,620 Jayne June 2, 1942 2,499,751 Hoza Mar. 7, 1950 FQREIGN PATENTS Number ,Country Date 371,445 Great Britain Apr. 25, 1932 371,779 Italy June 2, 1939 

